Hubcentric adapter question

[roccit_53 at scirocco.cs.uoguelph.ca (C Boyko)]

Okay, so I'm measuring some wheels for hubcentric rings. First, are our
stock hubs 57.1mm? That's what I'm getting with the calipers, just wanted
to confirm.

Second, using a variety of methods, I'm getting either 74 or 75mm for the
rim's "seat" diameter. I'd say 74.5 was the most accurate measurement, it's
tough because my calipers won't fit inside the rim, I used a depth guage,
it gave me a bit over 74mm, but it had a square end which won't set up
exactly at the rim, there's a teeny semicircular gap. And using my 73mm
rings and some plasticine, I get exactly 74.5mm each time. So should I
order the 74mm ring and not sweat the 0.5mm? I'd hate to get the 75 and not
have it go in the hole. I suppose anything's better than air...

Oh, and one more, what are the "normal" 14" tire sizes you guys are running. 

LMK what you think, I'd like to get the rings ordered ASAP.
cathy